Emergency services were called to the No 189 bus in Gloucester Place near the junction with Dorset Square at around 12.10am on Friday but were unable to save the life of the 48-year-old, who was pronounced dead at the scene.

Officers are now appealing to people who were travelling on the bus to contact them and help with their investigation.

Police believe they know the identity of the victim, but are awaiting formally identification and conformation next of kin have been informed.

The murder investigation is being led by Detective Chief Inspector Noel McHugh of the Homicide and Major Crime Command.

He said: “I believe the victim boarded the bus at Brent Cross bus station at 11.13pm on Thursday, 27 April.

“I want to hear from anyone who was at Brent Cross bus station or who travelled on the 189 bus from Brent Cross towards the Marylebone area at around that time.

“It is crucial that we speak with any potential witnesses.

"Even if you do not believe you saw anything significant, if you were at the bus station at around 11pm or on the bus then please call the incident room.”

Scotland Yard said there have been no arrests at this early stage and enquiries continue to establish the full circumstances.